Recently, since various devices requiring machine-to-machine (M2M) communication and high data transfer rate, such as smartphones or tablet personal computers (PCs), have appeared and come into widespread use, a data transfer rate of a wireless communication network has been rapidly increased. In order to satisfy the required high data transfer rate, recently, carrier aggregation (CA) technology which efficiently uses more frequency bands, cognitive ratio technology, multiple antenna technology for increasing data capacity in a restricted frequency, multiple base station cooperative transmission technology, etc. have been spotlighted.
In addition, a wireless communication network has evolved such that the density of accessible nodes is increased in the vicinity of a user. Here, the node refers to antennas or antenna groups spaced apart from each other by a predetermined distance or more in a distributed antenna system (DAS). However, the meaning of the node is not limited thereto and the node may have a wider meaning. That is, the node may include a picocell base station (PeNB), a home base station (HeNB), a remote radio head (RRH), a remote radio unit (RRU), a relay, distributed antennas (group), etc. A wireless communication system including nodes with high density may have higher system performance by cooperation between nodes. That is, unlike the case in which each node is an independent base station (BS), an advanced BS (ABS), a Node-B (NB), an eNode-B (eNB) or an access point (AP) which operates without cooperation, if one control station manages transmission and reception of each node such that each node operates as an antenna or antenna group for one cell, better system performance can be achieved. Hereinafter, a wireless communication system including a plurality of nodes is referred to as a multi-node system.
In a multi-node system, if each node performs scheduling and handover using an identifier (ID) thereof, the multi-node system may be regarded as a multi-cell system. In a multi-cell system, if the coverage areas of cells (that is, nodes) overlap, the multi-cell system is referred to as a multi-tier network.